Automotive vehicle manufacturers provide an original finish to vehicles that is typically one color overall or a two-tone finish. Sometimes, the original finish will have a contrasting wide stripe around the middle of the vehicle instead of having the two-tone finish of a contrasting color for the top half. There is a market, however, for customized, more colorful finishes, particularly as exterior finishes of vehicles with specially customized interiors, such as customized vans or trucks. More elaborate, customized finishes are provided by after-market refinishers.
Automotive refinish topcoats are generally applied in separate layers of basecoat and clearcoat to provide optimum match to the appearance of the original finish. Unlike the original finish coating compositions, which are typically cured at temperatures of 110° C. or higher, automotive refinish coatings must be formulated as either thermoplastic compositions or thermosetting compositions that cure at relatively low temperatures because many components of a finished vehicle cannot withstand high temperature bakes. Thermosetting refinish compositions, preferred as providing more durable and scratch- and mar-resistant coatings, are usually designed to cure at ambient temperatures, including by oxidation or radiation curing, or at low bakes. Although the coating may not develop full cure for hours or days, it is desirable to have the coating become “dry to handle” (that is, not tacky) within a reasonably short time. Shorter dry to handle times also reduce the chance that the coating could become contaminated with airborne particulates. This is particularly true for clearcoat compositions, which are not covered by other coatings layers and for which a smooth, unblemished surface is critical to obtaining the desired appearance.
For a customized finish, a variety of basecoat colors may be applied, usually in layers of diminishing area, to achieve the desired effect. A clearcoat layer is then applied over the entire vehicle. Adhesion of the refinish coatings to the original finish is critical. Typically, the original finish is scuff-sanded before the refinish coating layers are applied. Scuff-sanding is tedious and time-consuming, especially when the whole exterior of a large vehicle must be sanded, as is the case for customizing the finish of a van or truck. Areas may be missed, resulting in adhesion failure. It would be desirable to overcome this problem. Further, it is necessary, particularly in customizing vehicles, to ensure that the refinish clearcoat adheres well to the original finish.